#include <stdio.h>
#include <string.h>
#define N 100
int main()
{	   	   	  
    int n, i, j, k, len;
    char s1[N], s2[N], s3[2 * N];
    printf("main string:");
    gets(s1);
    printf("sub string:");
    gets(s2);
    len = strlen(s1);
    do
    {	   	   	  
        printf("site of beginning:(<=%d)", len);
        scanf("%d", &n);
    }
    while (n > len);
    for (i = 0; i < n; i++)
    {	   	   	  
        s3[i] = s1[i];
    }
    for (j = 0; s2[j] != '\0'; j++)
    {	   	   	  
        s3[i + j] = s2[j];
    }
    for (k = n; s1[k] != '\0'; k++)
    {	   	   	  
        s3[j + k] = s1[k];
    }
    s3[j + k] = '\0';
    printf("After instert:%s\n", s3);
    return 0;
}	